Oh dude, just let it go. Which woman would want a guy who had kissed her sister for whatever reason, not to mention said sister is the one who kept abusing her.
It's baffling how he never noticed Wendy was abused so bad, and even if he did, never really took action while treating her green tea sister with a high level of courtesy. He might be a 'good' guy, but he was never a good guy to her. A good guy doesn't necessarily mean a good lover.